A man rides his bike past the site of the future Transbay Terminal on 415 Mission St. in San Francisco, Calif. on Wednesday, June 25, 2015, 2014. The Transbay Terminal will not be able to open with a public rooftop park without the aide of the private sector.

Photo: James Tensuan, The Chronicle

A man rides his bike past the site of the future Transbay Terminal...

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Cranes at the site of the future Transbay Terminal are reflected in a Walgreens on Mission St. in San Francisco, Calif. on Wednesday, June 25, 2015, 2014. The Transbay Terminal will not be able to open with a public rooftop park without the aide of the private sector.

Photo: James Tensuan, The Chronicle

Cranes at the site of the future Transbay Terminal are reflected in...

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A construction worker passes through the site of the future Transbay Terminal at 415 Mission St. in San Francisco, Calif. on Wednesday, June 25, 2015, 2014. The Transbay Terminal will not be able to open with a public rooftop park without the aide of the private sector.

Photo: James Tensuan, The Chronicle

A construction worker passes through the site of the future...

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A man passes the outside of the future Transbay Terminal on 415 Mission St. in San Francisco, Calif. on Wednesday, June 25, 2015, 2014. The Transbay Terminal will not be able to open with a public rooftop park without the aide of the private sector.

Photo: James Tensuan, The Chronicle

A man passes the outside of the future Transbay Terminal on 415...

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Caution tape wraps around the site of the future Transbay Terminal at 414 Mission St. in San Francisco, Calif. on Wednesday, June 25, 2015, 2014. The Transbay Terminal will not be able to open with a public rooftop park without the aide of the private sector.

(06-30) 19:32 PDT SAN FRANCISCO -- The 2017 opening of the $37 million Transbay Transit Center Rooftop Park is back on - but how the city is going to pay for it is, like the green space itself, very much up in the air.

Less than a week after The Chronicle reported that cost overruns would delay the construction of the 5.4-acre elevated park until after the transit center opens, staffers from Mayor Ed Lee's administration say they will make sure the park opens at the same time at the Transit Center. That's scheduled for late 2017.

"We would like to find a different source of funding - that is what we are working on," Rich said.

One possible funding source could be the so-called "Mello Roos Community Facilities District," a special tax zone around the Transbay Transit Center where property owners pay higher tax rate in exchange for zoning that allows them to build taller buildings. On Monday the Board of Supervisors Land Use and Economic Development Committee voted to recommend that the Board of Supervisors vote to create the district. The full board will likely adopt it next week.

The funding of the park, however, could cause a bit of a dilemma, Supervisor Scott Wiener said Monday. While he supports the Rooftop Park, the Mello Roos money is supposed to pay for the rail extension to downtown from the Caltrain station at Fourth and King streets. That is in the second phase of the Transbay project. And in addition to the $37 million for the park, cost overruns to the transit center may require another $200 million to be shifted from the downtown extension, known as the DTX.

"I have a serious concern about the funding for the DTX," said Wiener. "If the $37 million for the park comes out of the Mello Roos, that is $37 million less for the downtown extension. You can see the pattern."

Supervisor Jane Kim added: "We know we will get phase one done but we don't want to do it at the expense of the most important part of phase two, which is DTX," said Kim.

Kim and mayoral staffers raised the possibility that a corporate sponsor could step forward to help foot the bill for the park in exchange for naming rights.

Given all the backlash against tech wealth in San Francisco these days, it might be a good idea for an executive from Twitter or Google or Airbnb to pony up some money for a signature park that could be for San Francisco what the Highline has been for Manhattan.

- J.K. Dineen

Locked up: Step by baby step, Visitation Valley's dream for the Schlage Lock site is becoming a reality.

The Board of Supervisors next week will vote on a development agreement that would allow developer Universal Paragon to build 1,679 units of new housing, along with a grocery store and two parks. The complex will replace the 20-acre former Schlage Lock manufacturing complex that closed in 1999.

At a supervisors subcommittee meeting Monday, Supervisor Malia Cohen said that after 13 years and 18 public meetings it was time to move the project forward.

Under the latest agreement with Universal Paragon, the amount of retail has been chopped in half to just under 47,000 square feet while the number of units was increased from 1,250 to 1,679. "The original plan was maybe too ambitious about how much retail could be supported in this part of town," said planner Claudia Flores.

The project will be affordable - at least by San Francisco's inflated standards. Prices will come in about $500 to $550 a square foot - about half the $1,100-a-square foot developers are getting in neighborhoods like the Mission, Castro, and Hayes Valley, according to Ken Rich, director of development for the Mayor's Office of Housing and Economic Development. The development will be 15 percent below market rate.

"We are all so conditioned to seeing all new construction that is uber-fancy and expensive, but there are different market conditions in different parts of the city," said Supervisor Scott Wiener. "It's very much the case that these units are going to be more naturally affordable than other market rate projects."

Universal Paragon is looking to build two-thirds condos and one-third rental units. A two bedroom would rent for about $2,700 a month, based on the current market.

Representatives from the building trades asked the committee to delay the vote until a project labor agreement is finalized, but the request was shot down.